Pregnancy-associated plasma protein A as a marker of acute coronary syndromes

The pro-atherogenic enzyme PAPP-A is active in eluates from human carotid and femoral atherosclerotic plaques

Background

Pregnancy-associated plasma protein-A (PAPP-A) regulates bioavailability of insulin-like growth factor 1 (IGF1) in various tissues by proteolytic cleavage of a subset of IGF-binding proteins (IGFBPs). Pre-clinical studies have established a role of PAPP-A in atherosclerosis and proposed that targeting the proteolytic activity of PAPP-A has therapeutic value.This study aimed to investigate whether human atherosclerotic plaques contain proteolytically active PAPP-A, a prerequisite for further considering PAPP-A as a therapeutic target in patients.

Methods

We obtained carotid (n = 9) and femoral (n = 11) atherosclerotic plaques from patients undergoing vascular surgery and incubated freshly harvested plaque tissue in culture media for 24 h. Subsequently, conditioned media were assayed for PAPP-A, STC2, IGFBP4, and IGF1 using immunoassays. Enzymatic activity of PAPP-A was assessed by its ability to process recombinant IGFBP4-IGF1 complexes - a specific substrate of PAPP-A - by Western blotting.

Results

PAPP-A and STC2 were detectable in conditioned media from both carotid and femoral plaques, with higher STC2 concentrations in eluates from carotid plaque incubations (p = 0.02). IGFBP4 and IGF1 were undetectable. Conditioned media from all 20 plaques exhibited PAPP-A proteolytic activity. However, no correlation between PAPP-A concentration and its proteolytic activity was observed, whereas the PAPP-A: STC2 molar ratio correlated with PAPP-A activity (R2 = 0.25, p = 0.03).

Conclusion

This study provides evidence for the presence of enzymatically active PAPP-A in atherosclerotic plaques and underscores the need for further investigating potential beneficial effects associated with targeting PAPP-A in atherosclerotic cardiovascular disease.

IGF Signaling in the Heart in Health and Disease

One of the most vital processes of the body is the cardiovascular system's proper operation. Physiological processes in the heart are regulated by the balance of cardioprotective and pathological mechanisms. The insulin-like growth factor system (IGF system, IGF signaling pathway) plays a pivotal role in regulating growth and development of various cells and tissues. In myocardium, the IGF system provides cardioprotective effects as well as participates in pathological processes. This review summarizes recent data on the role of IGF signaling in cardioprotection and pathogenesis of various cardiovascular diseases, as well as analyzes severity of these effects in various scenarios.

Investigation of cardiovascular risk parameters in adolescents with metabolic syndrome

BACKGROUND

Metabolic syndrome leading to type 2 diabetes mellitus and cardiovascular diseases is a chronic multifactorial syndrome, associated with low-grade inflammation status. In our study, we aimed at assessing the serum levels of follistatin (FST), pregnancy-associated plasma protein-A (PAPP-A), and platelet/endothelial cell adhesion molecule-1 (PECAM-1) in adolescent patients with metabolic syndrome.

METHODS

This study was performed in 43 (19 males, 24 females) metabolic syndrome adolescents and 37 lean controls matched for age and sex. The serum levels of FST, PECAM-1, and PAPP-A were measured by using ELISA method.

RESULTS

Serum FST and PAPP-A levels in metabolic syndrome were significantly higher than those of controls (p < 0.005 and p < 0.05). However, there was no difference in serum PECAM-1 levels between metabolic syndrome and control groups (p = 0.927). There was a significant positive correlation between serum FST and triglyceride (r = 0.252; p < 0.05), and PAPP-A and weight, (r = 0.252; p < 0.05) in metabolic syndrome groups. Follistatin was determined statistically significant in both univariate (p = 0,008) and multivariate (p = 0,011) logistic regression analysis.

CONCLUSIONS

Our findings indicated a significant relationship between FST and PAPP-A levels and metabolic syndrome. These findings offer the possibility of using these markers in diagnosis of metabolic syndrome in adolescents as the prevention of the future complications.

The Pregnancy-Associated Plasma Protein-A (PAPP-A) Story

Pregnancy-associated plasma protein-A (PAPP-A) was first identified in the early 1970s as a placental protein of unknown function, present at high concentrations in the circulation of pregnant women. In the mid-to-late 1990s, PAPP-A was discovered to be a metzincin metalloproteinase, expressed by many nonplacental cells, that regulates local insulin-like growth factor (IGF) activity through cleavage of high-affinity IGF binding proteins (IGFBPs), in particular IGFBP-4. With PAPP-A as a cell surface-associated enzyme, the reduced affinity of the cleavage fragments results in increased IGF available to bind and activate IGF receptors in the pericellular environment. This proteolytic regulation of IGF activity is important, since the IGFs promote proliferation, differentiation, migration, and survival in various normal and cancer cells. Thus, there has been a steady growth in investigation of PAPP-A structure and function outside of pregnancy. This review provides historical perspective on the discovery of PAPP-A and its structure and cellular function, highlights key studies of the first 50 years in PAPP-A research, and introduces new findings from recent years.

Postmortem biochemistry in deaths from ischemic heart disease

Ischemic heart disease (IHD) is one of the leading causes of morbidity and sudden cardiac death worldwide and is an important public health problem. The presence of ischemia in clinical applications can be detected by ECG, biochemical markers, and radiological methods. Myocardial infarction is also frequently encountered in forensic autopsies. Postmortem diagnosis is determined as a result of histopathological examinations and additional exclusionary examinations (toxicology, microbiology, etc.). However, routine histopathological examinations are insufficient, especially when death occurs in the early period of ischemia. It creates a problem for forensic pathologists and forensic medicine specialists in such cases of sudden cardiac death. Postmortem biochemistry is one of the important and promising disciplines in which forensic applications work in order to diagnose these cases correctly. The issue of whether biomarkers used in the diagnosis of myocardial infarction in clinical studies can be used reliably in postmortem cases has been discussed by forensic medicine researchers for some time. This manuscript aims to review and summarize biomarkers belonging to various categories that have been studied in IHD-related deaths, in biological fluids taken at autopsy, or in animal experiments. Our study shows that the postmortem use of biochemical markers in the diagnosis of IHD yields promising results. However, it should not be forgotten that postmortem biochemistry is different from clinical applications due to its dynamics and that the body causes unpredictable changes in markers in the postmortem process. Therefore, comprehensive studies are needed to evaluate the postmortem stability of these markers in different biological fluids, their significance among various causes of death, and whether they are affected by any variable (Cardiopulmonary resuscitation, Postmortem interval, medications, etc.) before they are routinely applied. It is suggested by the authors that the cut-off values of biomarkers whose significance has been proven by these studies should be determined and that they should be used in this way in routine applications.

The Stanniocalcin-PAPP-A-IGFBP-IGF Axis

The pappalysin metalloproteinases, PAPP-A and PAPP-A2, have emerged as highly specific proteolytic enzymes involved in the regulation of insulin-like growth factor (IGF) signaling. The only known pappalysin substrates are a subset of the IGF binding proteins (IGFBPs), which bind IGF-I or IGF-II with high affinity to antagonize receptor binding. Thus, by cleaving IGFBPs, the pappalysins have the potential to increase IGF bioactivity and hence promote IGF signaling. This is relevant both in systemic and local IGF regulation, in normal and several pathophysiological conditions. Stanniocalcin-1 and -2 were recently found to be potent pappalysin inhibitors, thus comprising the missing components of a complete proteolytic system, the stanniocalcin-PAPP-A-IGFBP-IGF axis. Here, we provide the biological context necessary for understanding the properties of this molecular network, and we review biochemical data, animal experiments, clinical data, and genetic data supporting the physiological operation of this branch as an important part of the IGF system. However, although in vivo data clearly illustrate its power, it is a challenge to understand its subtle operation, for example, multiple equilibria and inhibitory kinetics may determine how, where, and when the IGF receptor is stimulated. In addition, literally all of the regulatory proteins have suspected or known activities that are not directly related to IGF signaling. How such activities may integrate with IGF signaling is also important to address in the future.

PAPP-A-Specific IGFBP-4 Proteolysis in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

The insulin-like growth factors IGF-I and IGF-II-as well as their binding proteins (IGFBPs), which regulate their bioavailability-are involved in many pathological and physiological processes in cardiac tissue. Pregnancy-associated plasma protein A (PAPP-A) is a metalloprotease that preferentially cleaves IGFBP-4, releasing IGF and activating its biological activity. Previous studies have shown that PAPP-A-specific IGFBP-4 proteolysis is involved in the pathogenesis of cardiovascular diseases, such as ischemia, heart failure, and acute coronary syndrome. However, it remains unclear whether PAPP-A-specific IGFBP-4 proteolysis participates in human normal cardiomyocytes. Here, we report PAPP-A-specific IGFBP-4 proteolysis occurring in human cardiomyocytes derived from two independent induced pluripotent cell lines (hiPSC-CMs), detected both on the cell surface and in the cell secretome. PAPP-A was measured by fluoroimmune analysis (FIA) in a conditioned medium of hiPSC-CMs and was detected in concentrations of up to 4.3 ± 1.33 ng/mL and 3.8 ± 1.1 ng/mL. The level of PAPP-A-specific IGFBP-4 proteolysis was determined as the concentration of NT-IGFBP-4 proteolytic fragments using FIA for a proteolytic neo-epitope-specific assay. We showed that PAPP-A-specific IGFBP-4 proteolysis is IGF-dependent and inhibited by EDTA and 1,10-phenanthroline. Therefore, it may be concluded that PAPP-A-specific IGFBP-4 proteolysis functions in human normal cardiomyocytes, and hiPSC-CMs contain membrane-bound and secreted forms of proteolytically active PAPP-A.

Early Mid-pregnancy Blood-Based Proteins as Possible Biomarkers of Increased Infant Birth Size in Sex-Stratified Analyses

The objective of this study was to evaluate the associations of 92 maternal blood-based proteins with increased infant birth size. The study was performed at the Uppsala University Hospital, Sweden, and included 857 mother and child dyads. The mean age of the women was 30.3 years, and 53.2% were nulliparous. Blood samples were collected at mean 18 + 2 weeks' gestation, and the Olink cardiovascular II panel was used to measure 92 proteins, either known to be or suspected to be markers of cardiovascular and inflammatory disease in humans. Multiple linear regression models adjusted for maternal age, parity, pre-conception BMI, height, and smoking were performed to evaluate the association of each individual protein with infant birth size. We also performed sex-stratified analyses. Eight proteins (Matrix metalloproteinase-12 (MMP-12), Prostasin (PRSS8), Adrenomedullin (ADM), Pappalysin-1 (PAPP-A), Angiotensin-converting enzyme 2 (ACE2), Sortilin (SORT1), Lectin-like oxidized LDL receptor 1 (LOX-1), and Thrombomodulin (TM)) were associated with infant birth size after false discovery rate adjustment. In the analyses including only female infants, ten proteins (MMP-12, Growth/differentiation factor 2 (GDF-2), PRSS8, SORT1, ADM, Interleukin-1 receptor antagonist protein (IL-1ra), Leptin (LEP), ACE2, TM, and Tumor necrosis factor receptor superfamily member 11A (TNFRSF11A)) were associated with infant birth size. Two proteins (PAPP-A and PRSS8) were associated with infant birth size among male infants. Our study suggests several proteins as potential biomarkers for increased birth weight, and our findings could act as a base for future research to identify new potential markers that could be added to improve screening for large infants.

Integrating Mechanisms in Thrombotic Peripheral Arterial Disease

Peripheral arterial disease (PAD), a manifestation of systemic atherosclerosis, is underdiagnosed in the general population. Despite the extensive research performed to unravel its pathophysiology, inadequate knowledge exists, thus preventing the development of new treatments. This review aims to highlight the essential elements of atherosclerosis contributing to the pathophysiology of PAD. Furthermore, emphasis will be placed on the role of thrombo-inflammation, with particular focus on platelet and coagulation activation as well as cell-cell interactions. Additional insight will be then discussed to reveal the contribution of hypercoagulability to the development of vascular diseases such as PAD. Lastly, the current antithrombotic treatments will be discussed, and light will be shed on promising new targets aiming to aid the development of new treatments.

Emerging biomarkers for the detection of cardiovascular diseases

Background

The prevalence of cardiovascular disease (CVD) has been continuously increasing, and this trend is projected to continue. CVD is rapidly becoming a significant public health issue. Every year there is a spike in hospital cases of CVD, a critical health concern in lower- and middle-income countries. Based on identification of novel biomarkers, it would be necessary to study and evaluate the diagnostic requirements or CVD to expedite early detection.

Main body

The literature review was written using a wide range of sources, such as well-known medical journals, electronic databases, manuscripts, texts, and other writings from the university library. After that, we analysed the specific markers of CVD and compiled a systematic review. A growing body of clinical research aims to identify people who are at risk for cardiovascular disease by looking for biomolecules. A small number of biomarkers have been shown to be useful and reliable in medicine. Biomarkers can be used for a variety of clinical applications, such as predicting heart disease risk, diagnosing disease, or predicting outcomes. As a result of the ability for a single molecule to act as a biomarker, its usefulness in medicine is expected to increase significantly.

Conclusions

Based on assessing the current trends in the application of CVD markers, we discussed and described the requirements for the application of CVD biomarkers in coronary heart disease, cerebrovascular disease, rheumatic heart disease, and other cardiovascular illnesses. Furthermore, the current review focuses on biomarkers for CVD and the procedures that should be considered to establish the comprehensive nature of the expression of biomarkers for cardiovascular illness.

Structure of the proteolytic enzyme PAPP-A with the endogenous inhibitor stanniocalcin-2 reveals its inhibitory mechanism

The metzincin metalloproteinase PAPP-A plays a key role in the regulation of insulin-like growth factor (IGF) signaling by specific cleavage of inhibitory IGF binding proteins (IGFBPs). Using single-particle cryo-electron microscopy (cryo-EM), we here report the structure of PAPP-A in complex with its endogenous inhibitor, stanniocalcin-2 (STC2), neither of which have been reported before. The highest resolution (3.1 Å) was obtained for the STC2 subunit and the N-terminal approximately 1000 residues of the PAPP-A subunit. The 500 kDa 2:2 PAPP-A·STC2 complex is a flexible multidomain ensemble with numerous interdomain contacts. In particular, a specific disulfide bond between the subunits of STC2 and PAPP-A prevents dissociation, and interactions between STC2 and a module located in the very C-terminal end of the PAPP-A subunit prevent binding of its main substrate, IGFBP-4. While devoid of activity towards IGFBP-4, the active site cleft of the catalytic domain is accessible in the inhibited PAPP-A·STC2 complex, as shown by its ability to hydrolyze a synthetic peptide derived from IGFBP-4. Relevant to multiple human pathologies, this unusual mechanism of proteolytic inhibition may support the development of specific pharmaceutical agents, by which IGF signaling can be indirectly modulated.

Sex differences in proteomic correlates of coronary microvascular dysfunction among patients with heart failure and preserved ejection fraction

AIMS

Little information is available on sex differences in coronary microvascular dysfunction (CMD) in heart failure with preserved ejection fraction (HFpEF). We investigated sex-specific proteomic profiles associated with CMD in patients with HFpEF.

METHODS AND RESULTS

Using the prospective multinational PROMIS-HFpEF study (Prevalence of Microvascular Dysfunction in HFpEF; n = 182; 54.6% women), we compared clinical and biomarker correlates of CMD (defined as coronary flow reserve [CFR] <2.5) between men and women with HFpEF. We used lasso penalized regression to analyse 242 biomarkers from high-throughput proximity extension assays, adjusting for age, body mass index, creatinine, smoking and study site. The prevalence of CMD was similarly high in men and women with HFpEF (77% vs. 70%; p = 0.27). Proteomic correlates of CFR differed by sex, with 10 versus 16 non-overlapping biomarkers independently associated with CFR in men versus women, respectively. In men, proteomic correlates of CFR included chemokine ligand 20, brain natriuretic peptide, proteinase 3, transglutaminase 2, pregnancy-associated plasma protein A and tumour necrosis factor receptor superfamily member 14. Among women, the strongest proteomic correlates with CFR were insulin-like growth factor-binding protein 1, phage shock protein D, CUB domain-containing protein 1, prostasin, decorin, FMS-like tyrosine kinase 3, ligand growth differentiation factor 15, spondin-1, delta/notch-like epidermal growth factor-related receptor and tumour necrosis factor receptor superfamily member 13B. Pathway analyses suggested that CMD was related to the inflammation-mediated chemokine and cytokine signalling pathway among men with HFpEF, and the P13-kinase and transforming growth factor-beta signalling pathway among women with HFpEF.

CONCLUSION

While the prevalence of CMD among men and women with HFpEF is similar, the drivers of microvascular dysfunction may differ by sex. The current inflammatory paradigm of CMD in HFpEF potentially predominates in men, while derangement in ventricular remodelling and fibrosis may play a more important role in women.

Risk Assessment after ST-Segment Elevation Myocardial Infarction: Can Biomarkers Improve the Performance of Clinical Variables?

INTRODUCTION

Myocardial infarction with ST-segment elevation (STEMI) is the coronary artery disease associated with the highest risk of morbimortality; however, this risk is heterogeneous, usually being evaluated by clinical scores. Risk assessment is a key factor in personalized clinical management of patients with this disease.

AIM

The aim of this study was to assess whether some new cardiac biomarkers considered alone, combined in a multibiomarker model or in association with clinical variables, improve the short- and long-term risk stratification of STEMI patients.

MATERIALS AND METHODS

This was a retrospective observational study of 253 patients with STEMI. Blood samples were obtained before or during the angiography. The assessed biomarkers were C-terminal fragment of insulin-like growth factor binding protein-4 (CT-IGFBP4), high sensitive cardiac troponin T (hs-cTnT), N-terminal fragment of probrain natriuretic peptide (NT-proBNP), and growth differentiation factor 15 (GDF-15); they reflect different cardiovascular (CV) physiopathological pathways and underlying pathologies. We registered in-hospital and follow-up mortalities and their causes (cardiovascular and all-cause) and major adverse cardiac events (MACE) during a two year follow-up. Discrimination, survival analysis, model calibration, and reclassification of the biomarkers were comprehensively evaluated.

RESULTS AND DISCUSSION

In total, 55 patients (21.7%) died, 33 in-hospital and 22 during the follow-up, most of them (69.1%) from CV causes; 37 MACE occurred during follow-up. Biomarkers showed good prognostic ability to predict mortality, alone and combined with the multibiomarker model. A predictive clinical model based on age, Killip-Kimball class, estimated glomerular filtration rate (eGFR), and heart rate was derived by multivariate analysis. GDF-15 and NT-proBNP significantly improved risk assessment of the clinical model, as shown by discrimination, calibration, and reclassification of all the end-points except for all-cause mortality. The combination of NT-proBNP and hs-cTnT improved CV mortality prediction.

CONCLUSIONS

GDF-15 and NT-proBNP added value to the usual risk assessment of STEMI patients.

Pregnancy-associated plasma protein A mRNA expression as a marker for differentiated thyroid cancer: results from a "surgical" and a "cytological" series

PURPOSE

Pregnancy-associated plasma protein A (PAPPA) is a metalloproteinase initially described for its role during pregnancy. PAPPA regulates IGF ligands 1 (IGF1) bioavailability through the degradation of IGF-binding protein 4 (IGFBP4). After the cleavage of IGFBP4, free IGF1 is able to bind IGF1 receptors (IGF1R) triggering the downstream signaling. Recently, PAPPA expression has been linked with development of several cancers. No data have been published on thyroid cancer, yet.

METHODS

We evaluated PAPPA, insulin-like growth factor (IGF1), IGF1 receptors (IGF1R) and IGF-binding protein 4 (IGFBP4) mRNA expression levels in a "Surgical series" of 94 thyroid nodules (64 cancers, 16 follicular adenomas and 14 hyperplastic nodules) and in a "Cytological series" of 80 nodules from 74 patients underwent to fine-needle aspiration cytology (FNAC). In tissues, PAPPA was also evaluated by western blot.

RESULTS

We found that PAPPA expression was increased in thyroid cancer specimen at mRNA and protein levels and that, adenomas and hyperplastic nodules had an expression similar to normal tissues. When applied on thyroid cytologies, PAPPA expression was able to discriminate benign from malignant nodules contributing to pre-surgical classification of the nodules. We calculated a cut-off with a good specificity (91%) which reached 100% when combined with molecular biology.

CONCLUSION

These results show that PAPPA could represent a promising diagnostic marker for differentiated thyroid cancer.

Early brain injury and cognitive impairment after aneurysmal subarachnoid haemorrhage

The first 72 h following aneurysm rupture play a key role in determining clinical and cognitive outcomes after subarachnoid haemorrhage (SAH). Yet, very little is known about the impact of so called “early brain injury” on patents with clinically good grade SAH (as defined as World Federation of Neurosurgeons Grade 1 and 2). 27 patients with good grade SAH underwent MRI scanning were prospectively recruited at three time-points after SAH: within the first 72 h (acute phase), at 5–10 days and at 3 months. Patients underwent additional, comprehensive cognitive assessment 3 months post-SAH. 27 paired healthy controls were also recruited for comparison. In the first 72 h post-SAH, patients had significantly higher global and regional brain volume than controls. This change was accompanied by restricted water diffusion in patients. Persisting abnormalities in the volume of the posterior cerebellum at 3 months post-SAH were present to those patients with worse cognitive outcome. When using this residual abnormal brain area as a region of interest in the acute-phase scans, we could predict with an accuracy of 84% (sensitivity 82%, specificity 86%) which patients would develop cognitive impairment 3 months later, despite initially appearing clinically indistinguishable from those making full recovery. In an exploratory sample of good clinical grade SAH patients compared to healthy controls, we identified a region of the posterior cerebellum for which acute changes on MRI were associated with cognitive impairment. Whilst further investigation will be required to confirm causality, use of this finding as a risk stratification biomarker is promising.

Increase in Ischemia-Modified Albumin and Pregnancy-Associated Plasma Protein-A in COVID-19 Patients

This study was undertaken due to the urgent need to explore reliable biomarkers for early SARS-CoV-2 infection. We performed a retrospective study analyzing the serum levels of the cardiovascular biomarkers IL-6, TNF-α, N-terminal pro-B natriuretic peptide, cardiac troponin T (cTnT), ischemia-modified albumin (IMA) and pregnancy-associated plasma protein-A (PAPP-A) in 84 patients with COVID-19.Patients were divided into three groups according to their RT-qPCR and IgG values: acute infection (n = 35), early infection (n = 25) or control subjects (n = 24). Levels of biomarkers were analyzed in patient serum samples using commercially available ELISA kits. Results showed a significant increase in IMA and PAPP-A levels in the early infected patients. Moreover, multivariate analysis and receiver operating characteristic (ROC) curve showed that IMA and PAPP-A had excellent discrimination value for the early stage of COVID-19. For IMA, the area under the ROC curve (AUC) had a value of 0.94 (95% confidence interval (CI): 0.881–0.999). Likewise, the serum level of PAPP-A was significantly higher in patients with early infection than in the control subjects (AUC = 0.801 (95% CI: 0.673–0.929)). The combined use of IMA and PAPP-A enhanced the sensitivity for total SARS-CoV-2-infected patients to 93%. These results suggest that the increased levels of PAPP-A and IMA shed light on underlying mechanisms of COVID-19 physiopathology and might be used as efficient biomarkers with high sensitivity and specificity for the early stage of COVID-19. Importantly, when monitoring pregnancy and cardiovascular diseases using PAPP-A or IMA levels, a SARS-CoV-2 infection should be discarded for proper interpretation of the results.

Novel Cardiovascular Biomarkers Associated with Increased Cardiovascular Risk in Women With Prior Preeclampsia/HELLP Syndrome: A Narrative Review

Evidence has shown that women with a history of preeclampsia or haemolysis, elevated liver enzymes and low platelets (HELLP) syndrome have an increased risk of cardiovascular disease later in life. Recommendations for screening, prevention and management after such pregnancies are not yet defined. The identification of promising non-traditional cardiovascular biomarkers might be useful to predict which women are at greatest risk. Many studies are inconsistent and an overview of the most promising biomarkers is currently lacking. This narrative review provides an update of the current literature on circulating cardiovascular biomarkers that may be associated with an increased cardiovascular disease risk in women after previous preeclampsia/HELLP syndrome. Fifty-six studies on 53 biomarkers were included. From the summary of evidence, soluble fms-like tyrosine kinase-1, placental growth factor, interleukin (IL)-6, IL-6/IL-10 ratio, high-sensitivity cardiac troponin I, activin A, soluble human leukocyte antigen G, pregnancy-associated plasma protein A and norepinephrine show potential and are interesting candidate biomarkers to further explore. These biomarkers might be potentially eligible for cardiovascular risk stratification after preeclampsia/HELLP syndrome and may contribute to the development of adequate strategies for prevention of hypertension and adverse events in this population.

Metabolic improvement after gastric bypass correlates with changes in IGF-regulatory proteins stanniocalcin-2 and IGFBP-4

BACKGROUND

Pregnancy-associated plasma protein-A (PAPP-A) is an enzyme that increases IGF-activity through cleavage of IGF-binding proteins (IGFBPs), primarily IGFBP-4, whereby bound IGF-I becomes released as a free molecule. The enzymatic activity of PAPP-A is irreversibly suppressed by the glycoprotein stanniocalcin-2 (STC2). Pre-clinical and clinical studies suggest that the STC2 - PAPP-A - IGFBP-4 axis is important in controlling local IGF-action. STC2, PAPP-A and IGFBP-4 are expressed in adipose tissue, and as bariatric surgery markedly reduces the amount of fat, we found it relevant to study the impact of Roux-en-Y gastric bypass (RYGB) on circulating concentrations of this IGF-regulatory network.

METHODS

Analysis of fasting blood samples from 20 obese subjects, hereof 10 with preoperative type 2 diabetes, investigated before RYGB, and 1 week, 3 months and 12 months post-surgery. Members of the IGF-system were analyzed by immunoassays, bioactive IGF by cell-based IGF-I receptor activation assay. We compared changes in IGF-system components with changes in fasting plasma insulin and glucose, and HbA1c.

RESULTS

PAPP-A remained unchanged, but STC2 decreased following RYGB (p < 0.05). The PAPP-A substrate IGFBP-4 declined (p < 0.01), whereas levels of PAPP-A specific IGFBP-4 fragments increased (p < 0.05), indicating an increased PAPP-A enzymatic activity post-RYGB. Further, the reduction in intact IGFBP-4 correlated with increased levels of bioactive IGF (p < 0.05). In multivariable regression analyses, an improved glucose metabolism correlated with reductions in STC2 and IGFBP-4, and with increases in bioactive IGF and IGF-I (p < 0.05).

CONCLUSION

After 12 months, RYGB caused reduced serum concentrations of intact IGFBP-4 and STC2, whereas serum PAPP-A remained at pre-operative levels. However, concentrations of PAPP-A generated IGFBP-4 fragments increased, pointing to an overall increased PAPP-A enzymatic activity following RYGB. Notably, reductions in intact IGFBP-4 and STC2 associated with improvements in glucose metabolism. Therefore, we propose that STC2 and IGFBP-4 are involved in the metabolic improvement that follows RYGB.

IGFBP-4 Proteolysis by PAPP-A in a Primary Culture of Rat Neonatal Cardiomyocytes under Normal and Hypertrophic Conditions

Cardiovascular diseases (CVD) are among the leading causes of death and disability worldwide. Pregnancy-associated plasma protein-A (PAPP-A) is a matrix metalloprotease localized on the cell surface. One of the substrates that PAPP-A cleaves is the insulin-like growth factor binding protein-4 (IGFBP-4), a member of the family of proteins that bind insulin-like growth factor (IGF). Proteolysis of IGFBP-4 by PAPP-A occurs at a specific site resulting in formation of two proteolytic fragments - N-terminal IGFBP-4 (NT-IGFBP-4) and C-terminal IGFBP-4 (CT-IGFBP-4), and leads to the release of IGF activating various cellular processes including migration, proliferation, and cell growth. Increased levels of the proteolytic IGFBP-4 fragments correlate with the development of CVD complications and increased risk of death in patients with the coronary heart disease, acute coronary syndrome, and heart failure. However, there is no direct evidence that PAPP-A specifically cleaves IGFBP-4 in the cardiac tissue under normal and pathological conditions. In the present study, using a primary culture of rat neonatal cardiomyocytes as a model, we have demonstrated that: 1) proteolysis of IGFBP-4 by PAPP-A occurs in the conditioned medium of cardiomyocytes, 2) PAPP-A-specific IGFBP-4 proteolysis is increased when cardiomyocytes are transformed to a hypertrophic state. Thus, it can be assumed that the enhancement of IGFBP-4 cleavage by PAPP-A and hypertrophic changes in cardiomyocytes accompanying CVD are interrelated, and PAPP-A appears to be one of the activators of the IGF-dependent processes in normal and hypertrophic-state cardiomyocytes.

Evaluation of pregnancy-associated plasma protein-A and some inflammation markers for atherosclerosis in psoriasis patients

Introduction

Psoriasis is a common, chronic inflammatory disease of the skin. Although its relationship with cardiovascular risk factors is one of the main causes of mortality, the association between psoriasis and cardiovascular events is controversial.

Aim

The aim of this study is to measure the levels of hs-CRP and pregnancy-associated plasma protein-A (PAPP-A) related to atherosclerosis in patients with moderate-severe psoriasis and to evaluate their possible association with disease severity.

Material and methods

This study included 45 moderate-severe psoriasis patients without additional risk factors for cardiovascular disease and 45 healthy individuals as a control group.

Results

Serum PAPP-A levels in both groups were given as two different variables, detectable and non- detectable, based on a value of 0.004 U/lL. When PAPP-A levels were compared, there was no statistically significant difference between the groups.

Conclusions

The use of the PAPP-A test in the evaluation of early-stage atherosclerosis in moderate-severe psoriasis patients who do not have additional risk factors for cardiovascular diseases may not be sufficient.

The relationship between serum pregnancy-associated plasma protein-A level in patients with aortic valve stenosis: a case-control study

OBJECTIVE

Calcific aortic stenosis (AS) is the most common form of calcific aortic valve disease. Many matrix metalloproteinase (MMP) have been shown to be expressed in aortic sclerosis and contribute to valve fibrosis and calcification. We investigated the relationship between Pregnancy-Associated Plasma Protein-A (PAPP-A) and AS.

METHODS

Sixty-one patients who referred to our cardiology clinic having AS diagnosed with transthoracic echocardiography and thirty control subjects were included in this study. The patient group was divided into two groups as mild and moderate-severe AS in terms of echocardiography results. Levels of C-reactive protein (CRP), insulin-like growth factor-1 (IGF-1) and PAPP-A were measured.

RESULTS

There was statistically significant difference between the patient and control group for PAPP-A (p = 0.009). In addition, the difference between MPV, IGF-1 and PAPP-A levels of control and AS groups was found. We found that serum PAPP-A level was an independent predictor of AS (B = 0.107, p = 0.01) by logistic regression analysis. In linear regression analysis, a significant correlation was found for AS severity with MPV, IGF-1 and PAPP-A levels, respectively (p = 0.025, p = 0.004, p = 0.035). It was revealed that PAPP-A and IGF-1 were negatively correlated (r = -0.327, p = 0.002). Correlation of serum PAPP-A level with echocardiographic parameters was no observed.

CONCLUSION

The level of PAPP-A may be a marker used in diagnosis rather than a marker used to determine the severity of AS. Studies with larger patient populations may further explain the role of PAPP-A in the diagnosis and treatment of AS.

The Role of Matrix Metalloproteinases in the Progression and Vulnerabilization of Coronary Atherosclerotic Plaques

Extracellular matrix (ECM) plays an important role in the development and progression of atherosclerotic lesions. Changes in the ECM are involved in the pathophysiology of many cardiovascular diseases, including atherosclerosis. Matrix metalloproteinases (MMPs) are a family of zinc-dependent proteases, also known as matrixins, with proteolytic activity in the ECM, being responsible for the process of tissue remodeling in various systemic pathologies, including cardiac and vascular diseases. MMPs play an important role in maintaining normal vascular structure, but also in secondary cardiovascular remodeling, in the formation of atherosclerotic plaques and in their vulnerabilization process. In addition to the assigned effect of MMPs in vulnerable plaques, they have a well-defined role in post-infarction ventricular remodeling and in various types of cardiomyopathies, followed by onset of congestive heart failure, with repeated hospitalizations and death. The aim of this manuscript was to provide a summary on the role of serum matrix metalloproteinases in the process of initiation, progression and complication of atherosclerotic lesions, from a molecular level to clinical applicability and risk prediction in patients with vulnerable coronary plaques.

Distinct plasma biomarkers confirm the diagnosis of mastocytosis and identify increased risk of anaphylaxis

BACKGROUND

Mastocytosis encompasses a heterogeneous group of disorders characterized by accumulation of clonal mast cells (MCs) in the skin and/or internal organs. Patients typically present with a broad variety of recurrent mediator-related clinical symptoms, including severe anaphylaxis. However, not all patients with mastocytosis experience anaphylactic reactions.

OBJECTIVE

We sought to identify disease-specific biomarkers in plasma that could be used to predict patients with mastocytosis with increased risk of anaphylaxis.

METHODS

Nineteen patients (≥18 years) and 2 control groups (11 subjects with allergic asthma and 13 healthy volunteers without history of atopy) were recruited. In total, 248 plasma proteins were analyzed by Proximity Extension Assay using Olink Proseek Multiplex panels.

RESULTS

We identified 4 novel proteins, in addition to tryptase, E-selectin, adrenomedullin, T-cell immunoglobulin, and mucin domain 1, and CUB domain-containing protein 1/CD138 to be significantly increased in patients with mastocytosis compared with both patients with asthma and healthy controls. Furthermore, we investigated whether we could discriminate between patients with mastocytosis with or without anaphylaxis. In addition to tryptase, we identified 3 novel proteins, that is, allergin-1, pregnancy-associated plasma protein-A, and galectin-3, with significantly different levels in patients with mastocytosis with anaphylaxis compared with those without anaphylaxis.

CONCLUSIONS

Newly identified proteomic biomarkers may be used to predict patients with mastocytosis with increased risk of anaphylaxis.

Local IGF Bioactivity Associates with High PAPP-A Activity in the Pericardial Cavity of Cardiovascular Disease Patients

OBJECTIVE

Pregnancy-associated plasma protein-A (PAPP-A) has been suggested as a proatherogenic enzyme by its ability to locally increase insulin-like growth factor (IGF) activity through proteolytic cleavage of IGF binding protein-4 (IGFBP-4). Recently, stanniocalcin-2 (STC2) was discovered as an inhibitor of PAPP-A. This study aimed to investigate IGFBP-4, PAPP-A, and STC2 as local regulators of IGF bioactivity in the cardiac microenvironment by comparing levels in the pericardial fluid with those in the circulation of patients with cardiovascular disease.

METHODS

Plasma and pericardial fluid were obtained from 39 patients undergoing elective cardiothoracic surgery, hereof 15 patients with type 2 diabetes. Concentrations of IGF-I, intact and fragmented IGFBP-4, PAPP-A, and STC2 were determined by immunoassays and IGF bioactivity by a cell-based assay.

RESULTS

In pericardial fluid, the concentrations of total IGF-I, intact IGFBP-4, and STC2 were 72 ± 10%, 91 ± 5%, and 40 ± 24% lower than in plasma, while PAPP-A was 15 times more concentrated. The levels of the 2 IGFBP-4 fragments generated by PAPP-A and reflecting PAPP-A activity were elevated by more than 25%. IGF bioactivity was 62 ± 81% higher in the pericardial fluid than plasma. Moreover, pericardial fluid levels of both IGFBP-4 fragments correlated with the concentration of PAPP-A and with the bioactivity of IGF. All protein levels were similar in pericardial fluid from nondiabetic and diabetic subjects.

CONCLUSIONS

PAPP-A increases IGF bioactivity by cleavage of IGFBP-4 in the pericardial cavity of cardiovascular disease patients. This study provides evidence for a distinct local activity of the IGF system, which may promote cardiac dysfunction and coronary atherosclerosis.

Aberrant pregnancy-associated plasma protein-A expression in breast cancers prognosticates clinical outcomes

Elevated levels of pregnancy-associated plasma protein-A (PAPP-A) have been implicated in the pathogenesis of various malignancies, including breast cancers. Breast cancer is one of the most frequent carcinomas and is the second most common cancer type detected in women of child-bearing age. Throughout pregnancy PAPP-A is produced and secreted by the placental syncytiotrophoblast cells; co-incidentally pregnancy-associated breast cancers often have an aggressive clinical course. The components of the PAPP-A/IGF axis was assessed in a panel of breast cancer cell lines. Using neutralising antibodies the impact of PAPP-A/IGF axis on cell motility was evaluated. PAPP-A was expressed in four of the twelve breast cancer cell lines tested. Blocking PAPP-A and IGFBP4 with neutralising antibodies significantly decreased motiliy of MDA-MB-231 cells. Upregulation of PAPP-A expression in breast tumours resulted in a trend towards worse overall survival. Notably, PAPP-A expression also positively correlated with epithelial-to-mesenchymal transition markers. In conclusion, these results indicate that PAPP-A plays an important role in breast cancer progression and it may be a promising therapeutic target in breast cancer.

The importance of inflammatory biomarkers, IL-6 and PAPP-A, in the evaluation of asymptomatic apical periodontitis

To examine the use of IL-6 and PAPP-A along with the new imaging for scoring methods to determine the severity of apical periodontitis (AP). The scoring of disease severity in 121 patients with AP, using dental radiographs, was based on "The Apical Periodontitis Grading Scale" (APGS), as those having 1 tooth with AP and severity of 3-4 were classified as grade 1 (mild); those having > 1 tooth and severity of 3-4 as grade 2 (moderate) and those with at least one tooth with a severity of 5 as grade 3 (severe). 45 systematically and orally healthy volunteers were selected as the control group (grade 0). Dental demographic data of all participants were recorded. Besides, venous blood samples were collected to study their complete blood count and levels of IL-6 and PAPP-A. Both NLR and PAPP-A levels of the grade 3 AP patients were found significantly higher than those of the control group and grade 1 and grade 2 AP patients (2.55 ± 1.40 vs 1.98 ± 1.05, 1.94 ± 0.58 and 1.86 ± 0.50; 0.606 ± 0.211 vs 0.422 ± 0.273, 0.447 ± 0.224 and 0.436 ± 0.242, p < 0.01, respectively). AP grades identified by the new scoring system were moderately correlated with IL-6 levels (Spearman r = 0.4168, p < 0.001). The risk of patients with IL-6 levels above 12.5 pg/ml to develop AP (relative risk) was found to be 2.19 times higher than that in those with lower IL-6 levels (98% Cl 1.233-3.905, p < 0.0024). APGS classification suggested to determine AP severity was found to be significantly correlated with levels of inflammatory markers IL-6 and PAPP-A.

Implications of the PAPP-A-IGFBP-IGF-1 pathway in the pathogenesis and treatment of polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic diseases implicated in the development of end stage renal disease (ESRD). Although FDA has recently approved a drug against ADPKD, there is still a great need for development of alternative management strategies for ADPKD. Understanding the different mechanisms that lead to cystogenesis and cyst expansion in ADPKD is imperative to develop new therapies against ADPKD. Recently, we demonstrated that caloric restriction can prevent the development of cystic disease in animal models of ADPKD and through these studies identified a new role for pregnancy associated plasma protein-A (PAPP-A), a component of the insulin-like growth factors (IGF) pathway, in the pathogenesis of this disease. The PAPP-A-IGF pathway plays an important role in regulation of cell growth, differentiation, and transformation and dysregulation of this pathway has been implicated in many diseases. Several indirect studies support the involvement of IGF-1 in the pathogenesis of ADPKD. However, it was only recently that we described a direct role for a component of this pathway in pathogenesis of ADPKD, opening a new avenue for the therapeutic approaches for this cystic disease. The present literature review will critically discuss the evidence that supports the role of components of IGF pathway in the pathogenesis of ADPKD and discuss the pharmacological implications of PAPP-A-IGF axis in this disease.

The association between Matrix Metallo-proteinases-9 (MMP-9) gene family polymorphisms and risk of Coronary Artery Disease (CAD): a systematic review and meta-analysis

Background

We performed a systematic review and meta-analysis of the Matrix metalloproteinases (MMP)-9 (C1562T), MMP-9 (R279Q), MMP-9 (P574R) and MMP-9 (R668Q) polymorphisms and risk of Coronary Artery Disease (CAD).

Methods

After a systematic literature search, pooled odds ratio (OR) and their corresponding 95% confidence interval (CI) were used to evaluate the strength of the association.

Results

We identified 40 studies with 11,792 cases and 8280 controls for C1562T, 7 case-control studies with 5525 cases and 2497 controls for R279Q, 2 studies with 1272 cases and 785 controls for P574R, and 2 studies with 1272 cases and 785 controls for R668Q. MMP-9 (C1562T) polymorphism was associated with increased risk of CAD under dominant model (OR = 1.41, P < 0.001), recessive model (OR = 1.59, P < 0.001), allelic model (OR = 1.38, P < 0.001), TT vs. CC model (OR = 1.70, P < 0.001), and CT vs. CC model (OR = 1.35, P < 0.001). Moreover, the subgroup analysis based on the continent of the study populations in this SNP indicated strong significant association in Asians but not in Europeans. Subgroup analysis was not performed in Africa, America and Oceania, due to lack of sufficient data.

Conclusions

Our meta-analysis revealed that MMP-9 (C1562T) SNP conferred a susceptibility risk for CAD in the overall analysis and Asian population. The overall analysis and subgroup analysis of the other three SNPs reject the association between MMP-9 polymorphisms and the risk of CAD. Although the results should interpret with caution because of small sample size of included studies in these three SNPs.

Metalloproteinase PAPP-A regulation of IGF-1 contributes to polycystic kidney disease pathogenesis

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic cause of end-stage renal disease (ESRD). The treatment options for ADPKD are limited. We observed an upregulation in several IGF-1 pathway genes in the kidney of Pkd1RC/RC mice, a model of ADPKD. Pregnancy-associated plasma protein A (PAPP-A), a metalloproteinase that cleaves inhibitory IGF binding proteins (IGFBPs), increasing the local bioactivity of IGF-1, was highly induced in the kidney of ADPKD mice. PAPP-A levels were high in cystic fluid and kidneys of humans with ADPKD. Our studies further showed that PAPP-A transcription in ADPKD was mainly regulated through the cAMP/CREB/CBP/p300 pathway. Pappa deficiency effectively inhibited the development of cysts in the Pkd1RC/RC mice. The role of PAPP-A in cystic disease appears to be regulation of the IGF-1 pathway and cellular proliferation in the kidney. Finally, preclinical studies demonstrated that treatment with a monoclonal antibody that blocks the proteolytic activity of PAPP-A against IGFBP4 ameliorated ADPKD cystic disease in vivo in Pkd1RC/RC mice and ex vivo in embryonic kidneys. These data indicated that the PAPP-A/IGF-1 pathway plays an important role in the growth and expansion of cysts in ADPKD. Our findings introduce a therapeutic strategy for ADPKD that involves the inhibition of PAPP-A.

CT-IGFBP-4 as a novel prognostic biomarker in acute heart failure

Aims

Insulin‐like growth factor binding protein‐4 (IGFBP‐4) fragments have been shown to predict the risk of major adverse cardiovascular events, including segment‐elevation myocardial infarction, in patients with acute coronary syndrome. We evaluated the prognostic value of the carboxy‐terminal fragment of IGFBP‐4 (CT‐IGFBP‐4) for all‐cause mortality in emergency room patients with acute heart failure (AHF).

Methods and results

CT‐IGFBP‐4, N‐terminal pro brain natriuretic peptide (NT‐proBNP), and C‐reactive protein (CRP) were measured at admission from the lithium‐heparin plasma of 156 patients with AHF. All‐cause mortality was recorded for 1 year. Receiver operator characteristic (ROC) curves, Kaplan–Meier, and Cox proportional hazard ratio analyses were performed to evaluate the prognostic value of the various clinical variables, CT‐IGFBP‐4, NT‐proBNP, CRP, and their combinations. During 1 year of follow‐up, 52 (33.3%) patients died. CT‐IGFBP‐4 only weakly correlated with NT‐proBNP (Pearson correlation coefficient r = 0.16, P = 0.044) and did not correlate with CRP (r = 0.08, P = 0.35), emphasizing the different nature of these biomarkers. The receiver operator characteristic area under the curve (ROC AUC) of CT‐IGFBP‐4 for the prediction of all‐cause mortality (0.727) was significantly higher than that of NT‐proBNP (0.680, P = 0.045) and CRP (0.669, P = 0.016). The combination of CT‐IGFBP‐4, NT‐proBNP, and CRP predicted mortality significantly better (ROC AUC = 0.788) than any of the biomarkers alone (P < 0.01 for all). The addition of CT‐IGFBP‐4 to a clinical prediction model that included age, gender, systolic blood pressure, creatinine, and sodium levels, as well as the history of previous heart failure, coronary artery disease, and hypertension significantly improved the mortality risk prediction (ROC AUC 0.774 vs. 0.699, P = 0.025). Cox hazard analysis indicated that elevated CT‐IGFBP‐4 was independently associated with 1 year mortality (hazard ratio 3.26, P = 0.0008) after adjustment for age, gender, history of previous heart failure, coronary artery disease, hypertension, chronic kidney failure, history of diabetes, heart rate, haemoglobin, plasma sodium, NT‐proBNP, CRP, cystatin C, and elevated cardiac troponin I or T. Patients with increased levels of either two or three of the biomarkers CT‐IGFBP‐4, NT‐proBNP, and CRP had significantly higher mortality risk (adjusted hazard ratio 10.04, P < 0.0001) than patients with increased levels of one or none of the biomarkers.

Conclusions

CT‐IGFBP‐4 was independently associated with all‐cause mortality in patients with AHF. Compared with single biomarkers, the combination of CT‐IGFBP‐4, NT‐proBNP, and CRP improved the prediction of all‐cause mortality in patients with AHF.

Pregnancy Associated Plasma Protein-A as a Cardiovascular Risk Marker in Patients with Stable Coronary Heart Disease During 10 Years Follow-Up-A CLARICOR Trial Sub-Study

Elevated pregnancy-associated plasma protein A (PAPP-A) is associated with mortality in acute coronary syndromes. Few studies have assessed PAPP-A in stable coronary artery disease (CAD) and results are conflicting. We assessed the 10-year prognostic relevance of PAPP-A levels in stable CAD. The CLARICOR trial was a randomized controlled clinical trial including outpatients with stable CAD, randomized to clarithromycin versus placebo. The placebo group constituted our discovery cohort (n = 1.996) and the clarithromycin group the replication cohort (n = 1.975). The composite primary outcome was first occurrence of cardiovascular event or death. In the discovery cohort, incidence rates (IR) for the composite outcome were higher in those with elevated PAPP-A (IR 12.72, 95% Confidence Interval (CI) 11.0-14.7 events/100 years) compared to lower PAPP-A (IR 8.78, 8.25-9.34), with comparable results in the replication cohort. Elevated PAPP-A was associated with increased risk of the composite outcome in both cohorts (discovery Hazard Ratio (HR) 1.45, 95% CI 1.24-1.70; replication HR 1.29, 95% CI 1.10-1.52). In models adjusted for established risk factors, these trends were attenuated. Elevated PAPP-A was associated with higher all-cause mortality in both cohorts. We conclude that elevated PAPP-A levels are associated with increased long-term mortality in stable CAD, but do not improve long-term prediction of death or cardiovascular events when added to established predictors.

Pregnancy-associated plasma protein A as a predictor of all-cause mortality and cardiovascular events in patients with chronic kidney disease: a meta-analysis of prospective studies

INTRODUCTION

The aim of the study was to assess the association of elevated serum pregnancy associated plasma protein A (PAPP-A) and the risk of all-cause mortality, cardiovascular events and mortality due to infection in patients with chronic kidney disease (CKD).

MATERIAL AND METHODS

We systematically searched the Medline database up to March 2017. A random effects model was used to pool the relative risks (RRs) and their 95% confidence intervals (CIs). Sensitivity analysis and subgroup analysis were performed to explore the potential sources of heterogeneity.

RESULTS

Six studies involving 2034 subjects were included. The pooled RRs for the risk of all-cause mortality and cardiovascular events were 1.50 (95% CI: 1.17-1.92), 1.26 (95% CI: 0.95-1.69), respectively. Sensitivity analysis by excluding each individual study showed no influence on the main results. Subgroup analysis showed that age, male proportion, follow-up term, and assay methods were not modifiable factors.

CONCLUSIONS

Our study suggests that elevated serum PAPP-A is associated with the risk of all-cause mortality in patients with CKD.

Pregnancy-Associated Plasma Protein-A2 Is Associated With Mortality in Patients With Lung Cancer

Pregnancy-associated plasma protein-A (PAPP-A) and its homolog PAPP-A2 are enzymes that modulate the availability and mitogenic activity of insulin-like growth factor-I (IGF-I). PAPP-A has been implicated in numerous cancers but reports on PAPP-A2 in malignancy are non-existent. In a prospective observational study of 689 patients under suspicion of lung cancer, we examined levels of PAPP-A and PAPP-A2 and their relationship with mortality. Serum PAPP-A and PAPP-A2 concentrations were determined in pre-diagnostic blood samples using ELISA, and immunohistochemical staining of PAPP-A and PAPP-A2 was performed in malignant tissue from five operable patients. A total of 144 patients were diagnosed with lung cancer, whereas the diagnosis was rejected in 545 subjects, who served as a control group. PAPP-A2 concentrations were higher in patients with lung cancer [median (IQR): 0.33 (0.21-0.56) ng/mL] than in controls [0.27 (0.17-0.39) ng/mL], p < 0.001, whereas PAPP-A levels did not differ. Presence of PAPP-A and PAPP-A2 were confirmed in tumor specimens, and staining occurred in a heterogeneous pattern. Patients were observed for a median (range) of 7 (6; 8) years, during which 114 patients (79.2%) died. Patient mortality differed according to PAPP-A2 tertile (p < 0.001). PAPP-A2 was associated with mortality with an unadjusted hazard ratio (95% CI) per doubling in protein concentration of 1.30 (1.12; 1.53), p = 0.001. In a multivariable model adjusted for age, sex, and BMI, PAPP-A2 remained predictive of the endpoint with a hazard ratio per doubling in protein concentration of 1.25 (1.05; 1.48), p = 0.013. Collectively, PAPP-A2, but not PAPP-A, is elevated in patients with lung cancer and associated with mortality. This novel role of PAPP-A2 in cancer warrants further functional studies as well as validation in external cohorts.

Genetic architecture of subcortical brain structures in 38,851 individuals

Subcortical brain structures are integral to motion, consciousness, emotions and learning. We identified common genetic variation related to the volumes of the nucleus accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen and thalamus, using genome-wide association analyses in almost 40,000 individuals from CHARGE, ENIGMA and UK Biobank. We show that variability in subcortical volumes is heritable, and identify 48 significantly associated loci (40 novel at the time of analysis). Annotation of these loci by utilizing gene expression, methylation and neuropathological data identified 199 genes putatively implicated in neurodevelopment, synaptic signaling, axonal transport, apoptosis, inflammation/infection and susceptibility to neurological disorders. This set of genes is significantly enriched for Drosophila orthologs associated with neurodevelopmental phenotypes, suggesting evolutionarily conserved mechanisms. Our findings uncover novel biology and potential drug targets underlying brain development and disease.

Direct Immunoassay for Free Pregnancy-Associated Plasma Protein A (PAPP-A)

Background

Pregnancy-associated plasma protein A (PAPP-A), especially in its noncomplexed form (fPAPP-A), is linked to vulnerable atherosclerotic plaques and risk of cardiac events. An assay for sensitive detection of fPAPP-A has been lacking. Our aim was to develop and validate a direct fPAPP-A assay to meet this need.

Methods

Monoclonal antibodies binding exclusively fPAPP-A were produced by immunizing mice with recombinant PAPP-A. In the optimized immunoassay, we used an fPAPP-A–specific capture antibody together with a lanthanide-chelate–labeled monoclonal antibody recognizing all PAPP-A forms. The assay was evaluated with CLSI guidelines and compared to a 2-assay subtractive fPAPP-A approach. Clinical performance was assessed with acute coronary syndrome patients.

Results

The limits of detection and quantitation were 0.4 mIU/L and 1.3 mIU/L, respectively, and the assay was linear up to 1000 mIU/L (R2 = 0.999). Both serum and heparin plasma were suitable matrices, and the complexed form of PAPP-A caused no significant interference. Correlation between the developed assay and the 2-assay approach was fair (Pearson's r = 0.819). Median concentration in healthy individuals was 1.0 mIU/L. fPAPP-A concentration was higher in patients who had myocardial infarction or died during the 1-year follow-up period than in those who did not (1.13 mIU/L vs 0.82 mIU/L, P = 0.008, model adjusted with age and sex). fPAPP-A measured with this direct assay predicted this end point as well as (follow-up 1 year) or better (30 days) than the 2-assay fPAPP-A alone or in combination with cTnI.

Conclusions

The new assay enables sensitive and reliable measurement of low cardiac-related fPAPP-A concentrations from blood samples.

PAPP-A and the IGF system in atherosclerosis: what's up, what's down?

Pregnancy-associated plasma protein-A (PAPP-A) is a metalloproteinase with a well-established role in releasing bioactive insulin-like growth factor-1 (IGF-1) from IGF-binding protein-2, -4, and -5 by proteolytic processing of these. The IGF system has repeatedly been suggested to be involved in the pathology of atherosclerosis, and both PAPP-A and IGF-1 are proposed biomarkers and therapeutic targets for this disease. Several experimental approaches based on atherosclerosis mouse models have been undertaken to obtain causative and mechanistic insight to the role of these molecules in atherogenesis. However, reports seem conflicting. The literature suggests that PAPP-A is detrimental, while IGF-1 is beneficial. This raises important questions that need to be addressed. Here we summarize the various studies and discuss potential underlying explanations for this seemingly inconsistency with the objective of better understanding complexities and limitations when manipulating the IGF system in mouse models of atherosclerosis. A debate clarifying what's up and what's down is highly warranted going forward with the ultimate goal of improving atherosclerosis therapy by targeting the IGF system.

Pregnancy-Associated Plasma Protein A Induces Inflammatory Cytokine Expression by Activating IGF-I/PI3K/Akt Pathways

Pregnancy-associated plasma protein A (PAPP-A) was previously reported to be an inflammatory biomarker and a prognostic marker of acute coronary syndrome (ACS) and involved in the process of atherosclerosis and plaque rupture. However, the role of PAPP-A in inflammation is poorly understood. In this study, we aimed to investigate the role of PAPP-A in macrophage activation and inflammatory cytokine production. RAW264.7 macrophages were treated with or without PAPP-A. Reverse-transcriptase quantitative real-time PCR (RT-qPCR) and Western blot were performed to detect gene and protein expressions. The concentration of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in culture supernatants was determined by ELISA. Results showed that PAPP-A significantly stimulated the expression of MCP-1, TNF-α, and IL-6 at both transcriptional and translational levels in a dose-dependent and time-dependent manner. The secretion of these inflammatory cytokines by macrophages was also increased after PAPP-A treatment. Moreover, PAPP-A activated the IGF-I/PI3K/Akt signaling pathway in macrophages. The PAPP-A-mediated upregulation of MCP-1, TNF-α, and IL-6 mRNA and protein levels were strongly inhibited by PI3K inhibitors or IGF-IR siRNA, indicating that the upregulation of MCP-1, TNF-α, and IL-6 could involve the IGF-I/PI3K/Akt pathway. Together, this study demonstrates that PAPP-A activates the macrophage signaling pathway (IGF-I/PI3K/Akt), which drives the expression and production of inflammatory cytokines known to contribute to the initiation and progression of ACS. These findings indicate that PAPP-A may play a proinflammatory role in the pathophysiology of ACS and serve as a potential therapeutic target.

Association of Low Maternal Pregnancy-associated Plasma Protein A with Adverse Perinatal Outcome

The aim is to provide an overall view of the association of low pregnancy-associated plasma protein A (PAPP-A) levels with adverse perinatal outcomes. The available literature in PubMed/Medline regarding PAPP-A and adverse pregnancy outcomes was searched for related articles, including terms such as “PAPP-A,” “intrauterine growth restriction (IUGR),” “small for gestational age (SGA),” “stillbirth,” “adverse outcome,” and others. The fifth percentile is supported by many recent studies to be PAPP-A’s cutoff for adverse outcome detection and the increased risk seems to be extremely high below 0.2 PAPP-A MoM (multiple of the median). Apart from chromosomal abnormalities, preeclampsia, intrauterine fetal demise, and pregnancy loss have been associated with maternal serum PAPP-A. For results below the first centile, PAPP-A has a strong positive predictive value for SGA and IUGR. Except for its vital role on the cleavage of insulin-like growth factor binding proteins (IGFBP), PAPP-A has proven to be a reliable marker for prenatal screening. Even though PAPP-A as a single predictor proved to be valuable for the prediction of some adverse perinatal outcomes, in some cases, a combination of PAPP-A to other maternal serum markers led to an increase in detection rates. PAPP-A is a promising maternal serum marker for pregnancy outcome prediction with more studies needed in order for its potentials to be fully understood and exploited.

Pregnancy-Associated Plasma Protein A (PAPP-A) Concentration in Population of Healthy Young People: Interactions with Tobacco Smoke and Anti-oxidative Status

Pregnancy-associated plasma protein A (PAPP-A) is a high-molecular zinc-binding metalloproteinase that was first detected in the serum of pregnant women. It can also be detected in men and non-pregnant women. Recently, a growing interest in determining the concentration of PAPP-A as a marker of oxidative stress and atherosclerotic processes has been observed. Among the factors that could potentially influence the PAPP-A formation is the exposure to tobacco smoke. Some components of tobacco smoke have an immediate effect on the body and also direct influence on the cardiovascular system. The aim of this study was to evaluate the relation between PAPP-A concentration and either passive or active exposure to tobacco smoke in the population of medicine students (n = 152). The relation between PAPP-A concentration and chosen markers of inflammatory response and anti-oxidative processes was analyzed. The samples of serum, urine, and saliva were collected and main nicotine metabolites in urine samples were determined using ELISA technique. Comparison of the PAPP-A concentrations in the study group revealed that in the group of active smokers, the concentration of the protein was significantly higher than in the group of passive smokers (p = .04) and the group of not-exposed students (p = .006). PAPP-A concentration showed significant positive correlation with the values of FRAP and main nicotine metabolites. The evident influence of both active and passive tobacco smoke exposure on PAPP-A levels in the studied population of young people who in general are not included in the group of high-risk cardiovascular incidents, shows how important early prevention of anti-health behaviors is.

IGF-1 and cardiovascular disease

Atherosclerosis is an inflammatory arterial pathogenic condition, which leads to ischemic cardiovascular diseases, such as coronary artery disease and myocardial infarction, stroke, and peripheral arterial disease. Atherosclerosis is a multifactorial disorder and its pathophysiology is highly complex. Changes in expression of multiple genes coupled with environmental and lifestyle factors initiate cascades of adverse events involving multiple types of cells (e.g. vascular endothelial cells, smooth muscle cells, and macrophages). IGF-1 is a pleiotropic factor, which is found in the circulation (endocrine IGF-1) and is also produced locally in arteries (endothelial cells and smooth muscle cells). IGF-1 exerts a variety of effects on these cell types in the context of the pathogenesis of atherosclerosis. In fact, there is an increasing body of evidence suggesting that IGF-1 has beneficial effects on the biology of atherosclerosis. This review will discuss recent findings relating to clinical investigations on the relation between IGF-1 and cardiovascular disease and basic research using animal models of atherosclerosis that have elucidated some of the mechanisms underlying atheroprotective effects of IGF-1.

Protein biomarkers for cardiorenal syndrome

INTRODUCTION

The term cardiorenal syndrome (CRS) describes the progressive pathology and interactions that develop upon heart and kidney failure. The definition of CRS is not firmly established and has evolved gradually during the last decade. The main clinical challenges associated with CRS are the lack of tools for early disease diagnosis and the inability to predict the development of cardiorenal pathophysiology. Currently several biomarkers have been proposed for improving CRS patient management. However, validation studies are needed to implement these initial findings to the clinical setting. Areas covered: In this review the database PubMed was used for a literature search on the definition and classification of CRS as well as biomarkers for CRS diagnosis and prognosis. Expert opinion: A universally acceptable classification system for CRS is not available. Thus, acquiring mechanistic insights relative to the pathophysiology of the disease is challenging. Reported biomarkers include well-established markers for heart/renal dysfunction and inflammation. Some proteins expressed in both organs have also been associated with CRS, yet their link to disease pathophysiology and organ cross-talk is missing. Establishing the link between deregulated molecular pathways and CRS phenotypes is required to define biological relevance of existing findings and ultimately biology-driven markers and targets.

Pregnancy-associated plasma protein-a is associated with subclinical atherosclerosis in men with HIV infection

The pathophysiology of an early and accelerated atherosclerotic process is complex and multifactorial in HIV-infected men compared with HIV-non-infected men. Several biomarkers have been well studied in the detection of the early stage of atherosclerosis, but studies are limited in HIV-infected men. The objective of this study was to investigate the association between serum pregnancy-associated plasma protein-A (PAPP-A) and carotid intima-media wall thickness (CIMT) in asymptomatic HIV-infected men. This a case-control study group comprising 118 HIV-infected men and 60 age-matched and gender-matched HIV-non-infected men. Serum PAPP-A was measured using an ELISA kit and carotid IMT was evaluated by Doppler ultrasonography in all subjects. Statistical analysis included receiver-operating characteristic (ROC) analysis, Pearson correlation and logistic regression analysis. Serum PAPP-A level was significantly higher in HIV +CIMT+ group compared with HIV +CIMT group and HIV-CIMT- group. We found a positive correlation between PAPP-A and increased CIMT (r=0.737, p<0.0001), and a negative correlation between nadir CD4 T cell counts and increased CIMT (r=-0.526, p<0.001). In multivariate logistic regression analyses, PAPP-A, nadir CD4 T cell count and age were significantly associated with subclinical atherosclerosis (p<0.001, p=0.006 and p=0.032, respectively). In ROC analysis, PAPP-A levels of >3.70 µg/mL were associated with subclinical atherosclerosis in HIV+ men with a specificity of 100% and a sensitivity of 71% (area under the curve: 0.949, 95% CI 0.875 to 1.000, p<0.001). Serum PAPP-A level was strongly correlated with increased CIMT in HIV-infected men. PAPP-A might be used as an early biomarker to identify atherosclerosis in asymptomatic HIV-infected men.

Proteomic Discovery and Validation of the Confounding Effect of Heparin Administration on the Analysis of Candidate Cardiovascular Biomarkers

BACKGROUND

Several plasma proteins have been suggested as markers for a variety of cardiovascular conditions but fail to qualify in independent patient cohorts. This may relate to interference of medication on plasma protein concentrations. We used proteomics to identify plasma proteins that changed in concentration with heparin administration and therefore potentially may confound their evaluation as biomarkers in situations in which heparin is used.

METHODS

We used a proteomic approach based on isobaric tagging and nano-LC-MS/MS analysis to quantify several hundred proteins in a discovery study in which individual plasma samples from 9 patients at intravascular ultrasound follow-up 12 months after an acute myocardial infarction before heparin administration and 2, 15, and 60 min after heparin administration; we validated our findings in 500 individual plasma samples obtained at admission from patients with suspected ST segment elevation myocardial infarction (STEMI), of whom 363 were treated with heparin before admission.

RESULTS

In the discovery study, 25 of 653 identified plasma proteins displayed a changed concentration after heparin administration (Bonferroni-corrected P value at P &lt; 7.66 × 10−5). Fourteen of the proteins changed significantly among heparin-treated patients in the validation study (nominal significance level of P &lt; 6.92 × 10−5). Among heparin-affected proteins in both the discovery study and the validation study were midkine, spondin 1, secreted frizzled-like protein 1, lipoprotein lipase, and follistatin, all previously associated with STEMI.

CONCLUSIONS

Medications such as heparin administration given before blood sampling may confound biomarker discovery and should be carefully considered in such studies.